Lock-out system for party-line telephones.



N9- 833,29'7. PATENTED OCT. 16, 1906.

. M. BRUCE, JR. LOGK-OUT SY M FOR PARTY LINE TELEPHONBS. V v

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* J I I I I I I I H M I I I h wiw 31 wzwtoz UNITED STATES PATENT OFFICE.

WILLIAM M.-BRUCE,."JR.,'OF SPRINGFIELD, OHIO, ASSIGNOR, BY DIRECT ANDMESNE ASSIGNMENTS, TO THE SELECT TELEPHONE MANUFAC- TURING COMPANY. OFSPRINGFIELD, OHIO, A CORPORATION OF OHIO.

LOCK-OUT SYSTEM FOR PARTY-LINE T ELEPHONES.

Specification of Letters Patent.

Patented Oct. 16, 1906.

Application filed. October 5. 1905. Serial No 281.477.

T0- 11 whom it may concern:

Be it known that I, WILLIAM M.- BRUCE,

Jr. a citizen ofthe United States, residingat Springfield, in the countyof Clark and State of Ohio, .have invented certain new and useful.Improvements in Lock-Out Systems for Party-Line Telephones, of which thefollowingwis a specification.

y invention relates to improvementsin devices for securing secrecy inparty-line tel-' ephones, the object beingto rovide a simple andefiective device whic can be used with common battery metallic-circuittelephone systems and without the necessity'of ground connections, thearrangement and construction bein such thatany number of subscribers maye placed on a single line and thatwhen one subscriber removes histelephone for use all the other subscribers will be automatically lockedout and cannot use the line or hear the conversation on the line untilthe subscriber has again released the line by replacing his telephone innormal position.

My invention consists in the arrangement and construction of partshereinafter described, and pointed outin the claims.

' In the accompanying drawing, I have shown a diagrammatic viewof asingle line to ener which are attached several subscribers stations, theline beingconnected at the central station with the usualswitchboard-switch,

preferably of the ordinary spring-jack type,

the said line being supplied with a common battery through suitableimpedance-coils a and b. At the several subscribers" stations,.

e represents the ordinary telephone-hook; e an electromagnet. or relayplaced in a bridge by lines at across'the main line at. and adapted toreceive current from-the central from the hook c by closing the switch 6I provide around the electromagnet e a shunt circuit ff, including apush-button or handoperated switch f, an electric magnetic switch foperated by-the relay or electromagnet e and the usual subscriberstalking which is normally'closed, connection 9 to the line a,- includinga con-l denser 9?. The relay or :1 electromagnet e Set f From thehand-omb d Switch 1.

provide'a' second will preferablybe of greater resistance than the.talking Instrument of the subscriber.

B whenever the telephone isremoved when one subscriber has removed hishook all the other talking-circuits will be opened and will remain openuntil the subscriber has replaced his instrument on the hook.

"In the event that one subscriber would want-to talk to anothersubscriber on the same line by operating the switch f the subscriberstalking instruments will be thrown out of the direct shunt around therelay and will be put in the shunt g, including the condenser. Thecurrent irom the central energy will thus cease'to fiow through thesubscribers talking instrument, and thus sulficient current will passout on the line a b to operate any other relay on the line. The firstsubscriber, however, will be able to hear anyconversation on the linethrough the condenser g, as the alternating currents produced by thetransmitter in theinductioncoil of the talking-instrument will passthrough the condenser, while the direct current flowing from the batterywill not.

The operation of the deviceis thought to be clear from the above. Anysubscriber removing his telephone from the hook estab-- .lishesaconnection by hrough'the relay, which is bridged directly thecircuit-closer e across the line. This relay operates the switch f 2 and"closes the subscribers talking instrument in the shunt around therelay.

The bringin of the subscribers instrument into this ad itional or shuntcircuit will ab .sorb so muchof the current on the line a b.

that no other relay on the line may be .operated. ,If the subscriberdesires to talk with another subscriber on the same line,

with hi'stelephoneofi the hook hesignals,

said subscriber or notifies the o erator at the central'sta'tionto'signal him an immediately The pressing of the presses the switchfswitch* opens the shunt f to linea, but

- closes the; shunt through 9 and the condenser -gffgthusfcutting outthe subscriber's talking 4 'mstrumentafromthe energy'of the battery atthe central station, but establishes a shunt through thejcondenser whichenable the subscriber to hear when the, other subscriber is on the line,the alternating currents produced by the transmitter passingithrough thecondenser. The pressing of the switch f will not affect the holding ofthe sw tch f 2 by the magnet e as the'bridge containing this magnet isnot disturbed b the pressing of the switchf, and the stopping of theflow of current through the shunt around this thu's cutting out thecondenser and reestablishingthe shunt around the magnet c with theinstruments therein. The coming in of the second subscriber will closethe shunt around his relay, and thus prevent any other" :system, aseries of subscribers stations, a

relay from being operated until both of the telephones are again on thehook and the line While the shunt in normal condition. around the relaycontaining the talking instruments will absorb so much current as toprevent any other relay on the line from being operated, it will notprevent the relaymagnets from holding their armatures in the tern, anelectroma net at each subscribers station adapted toe bridged acrosstheline by the main telephone-switch, a normally 0 en shunt around saidelectromagnet inc uding the subscribers talking instruments,-

' and a circuit-closer in said shunt adapted to be moved to and hcldinclosed position by the electromagneticforce of said magnet and adaptedto be released when said magnet is denergized, the resistance 'of saidmagnet and the shunt aroundthe same being such as to absorb the current.from the central tele' hone-receiver, a relayssaaavenergy so as toprevent any other magnet on the line from being operated.

2. In a central-energy partydfiie telephonesystem, a series of statlonsincluding talking instruments, amain switch 0 erated by a adhpted to bebri ged acrossthe line by'the operation of said main telephone-switch, ashunt around said relay including the subscriberstalking outfit, and acircuit-closer in said shunt operated by'the electroma netic force ofsaid relay to hold said shunt c osed so long as the relay-magnet isenergized and to open said shunt when the 'relay-magnet is notenergized, said relay having greater resistancethan the. shunt aroundthe same, whereby I the operationof one relay and" the closing of i thetalking-circuit will revent the'operation ;of any other relay on t eline.

'3; In a central-energy party-line telephone relay adapted to be bridgedacross the line by the operation of the main telephoneswitch,anormallyopen jshunt around said relay, a circuit-closer operated by theelectromagnetici orceof said relay to close and j maintain the shuntaround the relay'so long as the relay-magnet is energized and to opensaid shunt when-said magnet is not ener-' switch, a s unt around saidrelay having two branches including the talking instruments, one 'ofsaidbranches going direct to the line and theother branch including acondenser, a circuit-closer operated by the electromagne'tic force ofthe relay to close and maintain

